Quadrature radio frequency mixer with low noise and low conversion loss

ABSTRACT

In one embodiment of the invention, a method for convolution of signals is disclosed including generating four phased half duty cycle clocks each being out of phase by a multiple of ninety degrees from the others; coupling the four phased half duty cycle clocks into a four phase half duty cycle mixer; and switching switches in the four phase half duty cycle mixer in response to the four phased half duty cycle clocks to convolve a differential input signal with the four phased half duty cycle clocks to concurrently generate a differential in-phase output signal and a differential quadrature-phase output signal on a dual differential output port.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/970,311, filed on Jan. 7, 2008.

FIELD

The embodiments of the invention relate generally to radio transmittersand radio receivers. More particularly, the embodiments of the inventionrelate to radio frequency (RF) mixers.

BACKGROUND

A radio frequency (RF) mixer is generally a three-port radio frequencycomponent that is used to change the frequency of one of the inputsignals. In a radio transmitter, an RF mixer may also be referred to asan upconverter. When used in a radio receiver, an RF mixer may also bereferred to as a downconverter.

An RF mixer may be an active component or a passive component. Toachieve a small scale size, an RF mixer typically uses an activecomponent formed of transistors receiving a power supply so that it maybe integrated into integrated circuits with other radio frequencycomponents and devices.

Referring now to background FIG. 1, a schematic symbol for an RF mixer100 is illustrated. The mixer 100 has two inputs ports LO, IF/RF and oneoutput port RF/IF. If being used as an upconverter, the input ports arelocal oscillating input port LO and intermediate frequency input port IFand the output port is radio frequency output port RF. If the mixer isbeing used as a down converter, the input ports are a local oscillatinginput port LO and a radio frequency input port RF, and the output portis an intermediate frequency output port IF. The LO port receives alocal oscillating signal from an oscillating signal source.

The purpose of a mixer is to change the frequency of a signal whilehopefully keeping everything else about the signal the same. In FIG. 1,a first signal is coupled into the IF/RF port of the mixer 100 atparticular frequency f₁. A carrier signal is coupled into the LO port ofthe mixer 100 at a second frequency (f₂). Two different output signalsare formed at the RF/IF output port of the mixer 100 that may beselectively used. For upconversion to a higher frequency output signal,the in-phase output signal with a frequency equal to the sum of the twoinput frequencies (f₁+f₂) is selected. For downconversion to a lowerfrequency output signal, the output signal with a frequency equal to thedifference between the two input frequencies (f₁−f₂) is selected.

For example, sound waves of voice are in a low frequency range of 20 to20,000 hertz. On the other hand, carrier frequencies of cellularcommunications systems are in much higher frequency bands, such as900,000,000 hertz. To talk on a cellular phone, for example, the voicefrequency needs to be upconverted to the cellular carrier frequency usedin cellular communications. One or more mixers are used to change thefrequency band or range of human voice to the frequency band of thecellular carrier frequency.

One important characteristic of a mixer is conversion gain. Conversiongain is the ratio of the amplitude of the output signal to the amplitudeof the input signal (not the local oscillating LO signal). Conversiongain may be expressed as a power ratio. If the conversion gain is lessthan one, a fraction, there is actually a loss through the mixer.

Another important characteristic of a mixer is its noise figure (NF).The noise figure for a mixer is determined by dividing thesignal-to-noise ratio (SNR) at the input port (not the local oscillatingLO input port) by the signal-to-noise ratio (SNR) at the output port ofthe mixer and converting the ratio into decibels.

Thus, a mixer can be improved by increasing the conversion gain andreducing the noise figure. By increasing the conversion gain andreducing the noise figure in a mixer, the requirements for other RFcomponents may be more relaxed leading to simpler designs using lessintegrated circuit die area and possibly power conserving designs withthe amplification of less noise.

BRIEF SUMMARY

The embodiments of the invention are summarized by the claims thatfollow below.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a background figure illustrating a schematic symbol of a radiofrequency mixer.

FIG. 2A is a functional block diagram of a first embodiment of a fourphase half (50%) duty cycle quadrature mixer system.

FIG. 2B is a schematic diagram illustrating an exemplary implementationof the mixer illustrated in the four phase half (50%) duty cyclequadrature mixer system of FIG. 2A.

FIGS. 3A-3D illustrate the switching activity of the switches in themixer shown in FIG. 2A, 2B in response to the four phased half dutycycle clocks.

FIGS. 4A-4D are waveform diagrams of the four phased half duty cycleclock or local oscillating signals illustrating each of four phases.

FIG. 5A is a functional block diagram of a second embodiment of a fourphase half (50%) duty cycle quadrature mixer system.

FIG. 5B is a schematic diagram illustrating an exemplary implementationof the mixer illustrated in the four phase half (50%) duty cyclequadrature mixer system of FIG. 5A.

FIGS. 6A-6D illustrate the switching activity of the switches in themixer shown in FIG. 5A, 5B in response to the four phased half dutycycle clocks.

FIGS. 7A-7D are waveform diagrams of the four phased half duty cycleclock or local oscillating signals illustrating each of four phases.

FIG. 8 illustrates a functional block diagram of a simplified radiosystem in which embodiments of the invention may be used

FIG. 9 illustrates different types of switches that may be applied inimplementing the quadrature mixers illustrated in FIGS. 2A and 5A.

DETAILED DESCRIPTION

In the following detailed description of the embodiments of theinvention, numerous specific details are set forth in order to provide athorough understanding of the present invention. However, it will beobvious to one skilled in the art that the embodiments of the inventionmay be practiced without these specific details. In other instances wellknown methods, procedures, components, and circuits have not beendescribed in detail so as not to unnecessarily obscure aspects of theembodiments of the invention.

Introduction

The embodiments of the invention include a method, apparatus and systemfor a balanced fifty percent duty cycle mixer with a transfer functionproviding low noise and low conversion loss.

A 25% duty cycle mixer generates very little noise and has a lowconversion loss, both of which are desirable qualities in RF mixers.However, a 25% duty cycle mixer suffers from having a very stringentrequirement of rise time and fall time of the signal on the localoscillator port. Additionally, it's very difficult to generate a wellcontrolled set of four 25% duty cycle rectangular waveforms foroperation of a 25% duty cycle mixer.

Thus, it is desirable to design a mixer that operates with squarewaveforms having a 50% duty cycle with an internally generated transferfunction of a 25% duty cycle mixer to achieve low noise and lowconversion loss.

Four Phase Half Duty Cycle Mixer System

Referring now to FIG. 2A, a functional block diagram of a firstembodiment of a four phase half (50%) duty cycle quadrature mixer system200 is illustrated.

The quadrature mixer system 200 includes a quadrature mixer 204. Themixer system 200 further includes an electrical (e.g., current orvoltage) differential signal source 202, a first embodiment of a fourphase half (50%) duty cycle quadrature mixer 204, a dual differentialelectrical (e.g., current or voltage respectively) load 206, and a fourphase clock generator or local oscillator 208 coupled together as shown.In an integrated circuit, conductive traces in one or more layers may beused to couple the elements of the system together. The four phase halfduty cycle quadrature mixer 204 may also be referred to as aseries-parallel double balanced switching mixer.

The electrical (e.g., current or voltage) differential signal source 202provides a differential current or voltage signal on RF-IN and RF-INbthat is proportional to an RF input signal or an IF input signal, forexample. The differential current or voltage signal is coupled into themixer 204.

The four phase half duty cycle mixer 204 has a double ended ordifferential input port 201 to receive the differential current orvoltage input signal on RF-IN and RF-INb. The mixer 204 has a dualdifferential in-phase/quadrature-phase output port 210 including a firstdifferential in-phase output port (BB-I, BB-Ib) 210A and a seconddifferential quadrature-phase output port (BB-Q, BB-Qb) 210B. The mixer204 further receives four phased half duty cycle clock signals LO-I,LO-Ib, LO-Q, and LO-Qb from the clock generator or local oscillators208.

The mixer 204 includes switches 211A-218A and switches 211B-218B coupledtogether as shown. Switches 211A-218A are respectively coupled in seriesto switches 211B-218B between the differential input port 201 and thedual differential output port 210 of the mixer 204 as shown. Forexample, switch 211A is coupled in series to switch 211B between theinput RF-IN and the output BB-I to form serially coupled switches211A-211B. Additionally, pairs of serially coupled switches are furthercoupled in parallel between the differential input port 201 and the dualdifferential output port 210 of the mixer 204 as shown. For example,serially coupled switches 211A-211B are coupled in parallel to seriallycoupled switches 217A-217B between the differential input port (RF-IN,RF-INb) 201 and the dual differential output port (BB-I) 210 of themixer 204 as shown.

Due to the coupling of the switches, the mixer 204 may also be referredto as a series-parallel switching mixer or a series-parallel doubledbalanced mixer. The mixer 204 may be considered a passive mixer astypically power is not directly supplied to the switches.

The switches 211A-218A and switches 211B-218B have a respective controlinput coupled to one of the four phased half duty cycle clock or localoscillating signals LO-I, LO-Ib, LO-Q, and LO-Qb as shown in FIG. 2A.The local oscillator signal LO-I is coupled to the control input ofswitches 211A, 212A, 215A, and 216A. The local oscillator signal LO-Ibis coupled to the control input of switches 213A, 214A, 217A, and 218A.The local oscillator signal LO-Q is coupled to the control input ofswitches 212B, 213B, 216B, and 217B. The local oscillator signal LO-Qbis coupled to the control input of switches 211B, 214B, 215B, and 218B.

The switching activity of the switches 211A-218A and switches 211B-218Bin response to the four phased half duty cycle clock or localoscillating signals LO-I, LO-Ib, LO-Q, and LO-Qb is described withreference to FIGS. 3A-3D and 4A-4D. The switching activity of theswitches in the mixer 204 in response to the four phased half duty cycleclocks, convolves/multiplies the differential input signal with the fourphased half duty cycle clocks in the time/frequency domain toconcurrently generate a differential in-phase (I) signal on the in-phasedifferential output 210A and a differential quadrature-phase (Q) signalon the quadrature-phase differential output 210B. With the differentialin-phase (I) signal and the differential quadrature-phase (Q) signalbeing concurrently generated by the same mixer 204, less circuit areamay used and improvements in the performance of the mixer can beobtained.

The dual differential electrical (e.g., current or voltage respectively)load 206 is coupled to the dual differential in-phase/quadrature-phaseoutput port 210 of the mixer 204. If the differential signal source 202is providing a differential current signal source, the dual differentialelectrical load 206 is a current type loading so that current flows as asignal through the mixer from the differential input port to the dualdifferential output port. If the differential signal source 202 isproviding a differential voltage signal source, the load 206 is avoltage type loading so a voltage presented as a signal at thedifferential input port is coupled through the mixer to the differentialoutput port.

The dual differential output load 206 not only provides the proper loadsit may also convert the differential input signals into single endedoutput signals. That is the differential in-phase output signal (BB-I,BB-Ib) may be converted into the in-phase output signal I and thedifferential quadrature-phase output signal (BB-Q, BB-Qb) may beconverted into the quadrature-phase output signal Q.

As a current or voltage may be used with the mixer 204, the differentialcurrent or voltage source 202 may be referred to as an electricaldifferential signal source 202 and the dual differential current orvoltage load 206 may be referred to as a dual differential electricalload 206.

Referring now to FIG. 5A, a functional block diagram of a secondembodiment of a four phase half (50%) duty cycle quadrature mixer system500 is illustrated. The system 500 includes an electrical (e.g., currentor voltage) differential signal source 202, a second embodiment of afour phase half (50%) duty cycle quadrature mixer 504, a dualdifferential electrical (e.g., current or voltage respectively) load206, and a four phase clock generator or local oscillator 208 coupledtogether as shown. The four phase half duty cycle quadrature mixer 504may also be referred to as a cascaded double balanced switching mixer.

The electrical differential signal source 202, the dual differentialelectrical load 206, and the four phase clock generator 208 aredescribed elsewhere herein with the same reference numbers, thedescription of which is incorporated here by reference for reasons ofbrevity. The architecture of the second embodiment of the four phasehalf (50%) duty cycle mixer 504 differs from the architecture of thefirst embodiment of the four phase half (50%) duty cycle mixer 204.

The four phase half duty cycle mixer 504 has a double ended ordifferential input port 201 to receive the differential current orvoltage input signal on RF-IN and RF-INb. The mixer 504 has a dualdifferential output port 210 including a first in-phase (I) differentialoutput port (BB-I, BB-Ib) 210A and a second quadrature-phase (Q)differential output port (BB-Q, BB-Qb) 210B. The mixer 504 furtherreceives the four phased half duty cycle clock signals LO-I, LO-Ib,LO-Q, and LO-Qb from the clock generator 208.

The mixer 504 includes first level switches 511-514 and second levelswitches 521A-524A and 521B-524B coupled together as shown. Switches511-514, coupled in parallel to the differential input port 201, are ata first level of switches in the mixer and coupled in series torespective pairs of parallel switches 521A-521B, 522A-522B, 523A-523B,524A-524B, coupled in parallel to the dual differentialin-phase/quadrature-phase output port, at a second level of switches inthe mixer. In the mixer, the first level of switches cascade intorespective second level of switches between the differential input port201 and the dual differential I and Q output port 210. For example, theoutput of switch 511 couples in series to the input of the pair ofparallel switches 521A-521B. The output of switch 512 couples in seriesto the input of the pair of parallel switches 522A-522B. The output ofswitch 513 couples in series to the input of the pair of parallelswitches 523A-523B. The output of switch 514 couples in series to theinput of the pair of parallel switches 524A-524B.

More particularly, switches 511,521A are coupled in series between thedifferential input port (RFIN) 201 and the in-phase differential outputport (BB-I) 210A. Switches 511,521B are coupled in series between thedifferential input port (RFIN) 201 and the quadrature-phase differentialoutput port (BB-Q) 210B.

Switches 512,522A are coupled in series between the differential inputport (RFIN) 201 and the in-phase differential output port (BB-Ib) 210A.Switches 512,522B are coupled in series between the differential inputport (RFIN) 201 and the quadrature-phase differential output port(BB-Qb) 210B.

Switches 513,523A are coupled in series between the differential inputport (RFINb) 201 and the in-phase differential output port (BB-Ib) 210A.Switches 513,523B are coupled in series between the differential inputport (RFINb) 201 and the quadrature-phase differential output port(BB-Qb) 210B.

Switches 514,524A are coupled in series between the differential inputport (RFINb) 201 and the in-phase differential output port (BB-I) 210A.Switches 514,524B are coupled in series between the differential inputport (RFINb) 201 and the quadrature-phase differential output port(BB-Q) 210B.

Due to the coupling of the switches, the mixer 504 may also be referredto as a cascade switching mixer or a cascade doubled balanced switchingmixer. The mixer 504 may be considered a passive mixer as typicallypower is not directly supplied to the switches.

The switches 511-514, 521A-524A, 521B-524B have a respective controlinput coupled to one of the four phased half duty cycle clock or localoscillating signals LO-I, LO-Ib, LO-Q, and LO-Qb as shown in FIG. 5A.The first level of switches 511-514 generally have either the LO-I orLO-Ib local oscillating signals coupled to their control inputs. Thelocal oscillator signal LO-I is coupled to the control input of switches511 and 513. The local oscillator signal LO-Ib is coupled to the controlinput of switches 512 and 514. The second level of switches 521A-524Aand 521B-524B have either the LO-Q or LO-Qb local oscillating signalscoupled to their control inputs. The local oscillator signal LO-Q iscoupled to the control input of switches 521B, 522A, 523B, and 524A. Thelocal oscillator signal LO-Qb is coupled to the control input ofswitches 521A, 522B, 523A, and 524B.

The switching activity of the first level switches 511-514 and thesecond level switches 521A-524A,521B-524B in response to the four phasedhalf duty cycle clock or local oscillating signals LO-I, LO-Ib, LO-Q,and LO-Qb is described with reference to FIGS. 6A-6D and 7A-7D. Theswitching activity of the switches in the mixer 504 in response to thefour phased half duty cycle clocks, convolves/multiplies thedifferential input signal with the four phased half duty cycle clocks inthe time/frequency domain to concurrently generate a differentialin-phase (I) signal on the in-phase differential output 210A of the dualdifferential in-phase/quadrature-phase output port 210 and adifferential quadrature-phase (Q) signal on the quadrature-phasedifferential output 210B of the dual differentialin-phase/quadrature-phase output port 210. With the differentialin-phase (I) signal and the differential quadrature-phase (Q) signalbeing concurrently generated by the same mixer 504, less circuit areamay used and improvements in the performance of the mixer can beobtained.

The current or voltage load 206 is coupled to the dual differentialin-phase/quadrature-phase output port 210 of the mixer 504.

Four Phased Half Duty Cycle Clock Signals

The clock generator 208 generates the four phased half duty cycle clockor local oscillating signals LO-I, LO-Ib, LO-Q, and LO-Qb such as shownin FIGS. 4A-4D and 7A-7D. The four phased half duty cycle clock or localoscillating signals LO-I, LO-Ib, LO-Q, and LO-Qb are each out of phasefrom each other by a multiple of ninety degrees. For example, the localoscillating signal LO-I is out of phase from the local oscillatingsignal LO-Q by a multiple of one or ninety degrees. The localoscillating signal LO-I is out of phase from the local oscillatingsignal LO-Ib by a multiple of two or one-hundred eighty degrees. Thelocal oscillating signal LO-I is out of phase from the local oscillatingsignal LO-Qb by a multiple of three or two-hundred seventy degrees. Thefour phased half duty cycle clock or local oscillating signals LO-I,LO-Ib, LO-Q, and LO-Qb are each a square waveform with a fifty percent(50%) duty cycle.

Referring now to FIGS. 4A, 7A, a first phase 401 is generated by theclock generator 208. In the first phase 401, the local oscillatingsignals LO-I and LO-Qb are logically high (e.g., a logical one) and thelocal oscillating signals LO-Q and LO-Ib are logically low (e.g., alogical zero).

Referring now to FIGS. 4B, 7B, a second phase 402 is generated by theclock generator 208. In the second phase 402, the local oscillatingsignals LO-I and LO-Q are logically high (e.g., a logical one) and thelocal oscillating signals LO-Qb and LO-Ib are logically low (e.g., alogical zero).

Referring now to FIGS. 4C, 7C, a third phase 403 is generated by theclock generator 208. In the third phase 403, the local oscillatingsignals LO-Ib and LO-Q are logically high (e.g., a logical one) and thelocal oscillating signals LO-Qb and LO-I are logically low (e.g., alogical zero).

Referring now to FIGS. 4D, 7D, a fourth phase 404 is generated by theclock generator 208. In the fourth phase 404, the local oscillatingsignals LO-Ib and LO-Qb are logically high (e.g., a logical one) and thelocal oscillating signals LO-Q and LO-I are logically low (e.g., alogical zero).

Four Phase Half Duty Cycle Mixer Operation

The operation of the first embodiment of the four phase half duty cyclemixer 204 is now described with reference to FIGS. 3A-3D and 4A-4D.

Generally, the four phased half duty cycle clocks (LO-I, LO-Ib, LO-Q,LO-Qb) are generated with each being out of phase by a multiple ofninety degrees from the others. The four phased half duty cycle clocksare coupled into a four phase half duty cycle mixer 204. The switches inthe four phase half duty cycle mixer are switched in response to thefour phased half duty cycle clocks to convolve a differential inputsignal 201 with the four phased half duty cycle clocks to concurrentlygenerate a differential in-phase output signal I and a differentialquadrature-phase output signal Q on the dual differential output port(BB-I, BB-Ib) (BB-Q, BB-Qb) 210.

Referring to FIGS. 2A, 3A, and 4A, in the first phase 401 with the localoscillating signals LO-I and LO-Qb logically high (e.g., a logical one),switches 211A-211B are both respectively closed such that RF-IN passesthrough the mixer 204 to the BB-I output coupled into the load 206.Switches 215A-215B are also closed such that RF-INb passes through themixer 204 to the BB-Ib output coupled into the load 206.

Referring to FIGS. 2A, 3B, and 4B, in the second phase 402 with thelocal oscillating signals LO-I and LO-Q logically high (e.g., a logicalone), switches 212A-212B are both closed such that RF-IN passes throughthe mixer 204 to the BB-Q output coupled into the load 206. Switches216A-216B are both also closed such that RF-INb passes through the mixer204 to the BB-Qb output coupled into the load 206.

Referring to FIGS. 2A, 3C, and 4C, in the third phase 403 with the localoscillating signals LO-Ib and LO-Q logically high (e.g., a logical one),switches 213A-213B are both closed such that RF-IN passes through themixer 204 to the BB-Ib output coupled into the load 206. Switches217A-217B are both also closed such that RF-INb passes through the mixer204 to the BB-I output coupled into the load 206.

Referring to FIGS. 2A, 3D, and 4D, in the fourth phase 404 with thelocal oscillating signals LO-Ib and LO-Q logically high (e.g., a logicalone), switches 214A-214B are both closed such that RF-IN passes throughthe mixer 204 to the BB-Qb output coupled into the load 206. Switches218A-218B are both also closed such that RF-INb passes through the mixer204 to the BB-Q output coupled into the load 206.

The four phases of the local oscillating signals are generated over andover again to repeat the switching sequence of the transistors in themixer 204 and the respective paths through the mixer.

The operation of the second embodiment of the four phase half duty cyclemixer 504 is now described with reference to FIGS. 6A-6D and 7A-7D.

Referring to FIGS. 5A, 6A, and 7A, in the first phase 401 with the localoscillating signals LO-I and LO-Qb logically high (e.g., a logical one),switches 511,521A are both respectively closed such that the positive RFinput terminal RF-IN passes through the mixer 504 to the positivein-phase output terminal BB-I which is coupled into the load 206.Switches 513,523A are also closed such that negative RF input terminalRF-INb passes through the mixer 504 to the negative in-phase outputterminal BB-Ib coupled into the load 206.

Referring to FIGS. 5A, 6B, and 7B, in the second phase 402 with thelocal oscillating signals LO-I and LO-Q logically high (e.g., a logicalone), switches 511,521B are both closed such that the positive RF inputterminal RF-IN passes through the mixer 504 to the positivequadrature-phase output terminal BB-Q coupled into the load 206.Switches 513,523B are both also closed such that the negative RF inputterminal RF-INb passes through the mixer 504 to the negativequadrature-phase output terminal BB-Qb coupled into the load 206.

Referring to FIGS. 5A, 6C, and 7C, in the third phase 403 with the localoscillating signals LO-Ib and LO-Q logically high (e.g., a logical one),switches 512,522A are both closed such that positive RF input terminalRF-IN passes through the mixer 504 to the negative in-phase outputterminal BB-Ib coupled into the load 206. Switches 514,524A are bothalso closed such that the negative RF input terminal RF-INb passesthrough the mixer 504 to the positive in-phase output terminal BB-Icoupled into the load 206.

Referring to FIGS. 5A, 6D, and 7D, in the fourth phase 404 with thelocal oscillating signals LO-Ib and LO-Q logically high (e.g., a logicalone), switches 512,522B are both closed such that positive RF inputterminal RF-IN passes through the mixer 504 to the negativequadrature-phase output terminal BB-Qb coupled into the load 206.Switches 514,524B are both also closed such that the negative RF inputterminal RF-INb passes through the mixer 504 to the positivequadrature-phase output terminal BB-Q coupled into the load 206.

Switches

Referring now to FIG. 9, a plurality of switches are illustrated whichmay be applied in implementing the mixers 204, 504. Each of the switches211A-218B in the mixer 204 illustrated in FIG. 2A and each of theswitches 511-514, 521A-524A, 521B-524B illustrated in FIG. 5A are idealswitches. An ideal switch 901 is illustrated in FIG. 9. The ideal switch901 has a control input terminal C, an input terminal IN, and an outputterminal OUT. In the mixers 204, 504, the control input C is coupled toone of the four phased half duty cycle local oscillator or four phasedhalf duty cycle clock signals. The ideal switch is closed coupling theinput terminal IN to the output terminal OUT by a positive polarity of arespective one of the four phased half duty cycle clock or localoscillating signals LO-I, LO-Ib, LO-Q, and LO-Qb such as shown in FIGS.4A-4D and 7A-7D.

Instead of ideal switches 901 being used as the switches in the mixer204 and the mixer 504, different types of transistor switches may beused as the switches in the mixers.

For example, a first group or type of transistor switches may be usedthat are closed by the application of a high voltage level upon theircontrol terminal and opened by the application of a low voltage levelupon their control terminal The first type of transistor switch includesan n-channel field effect transistor (NFET) 903, an n-type junctionfield effect transistor (JFET) 907, and an NPN bipolar junctiontransistor (BJT) 909 that may be used as the switches in theimplementation of the mixers 204,504. Thus, the first type of transistorswitch is closed by a positive polarity of a respective one of the fourphased half duty cycle clock or local oscillating signals LO-I, LO-Ib,LO-Q, and LO-Qb such as shown in FIGS. 4A-4D and 7A-7D to a allowcurrent to flow across its poles (e.g., source and drain or collectorand emitter) at the appropriate time.

Alternatively, a second group or type of transistor switches may be usedthat close with the application of a low voltage level upon theircontrol terminals and open with the application of a high voltage levelupon their control terminals. The second group or type of transistorswitch includes a p=channel field effect transistor (PFET) 902, a p-typejunction field effect transistor (JFET) 906, and a PNP bipolar junctiontransistor (BJT) 908 that may be used as the switches in theimplementation of the mixers 204,504. Thus, the second group or type oftransistor switch is closed by a negative polarity of a respective oneof the four phased half duty cycle clock or local oscillating signalsLO-I, LO-Ib, LO-Q, and LO-Qb to a allow current to flow across its poles(e.g., source and drain or collector and emitter). That is, therespective positive polarity of the four phased half duty cycle clock orlocal oscillating signals LO-I, LO-Ib, LO-Q, and LO-Qb is inverted andcoupled to the control terminal (e.g., gate) of the second group or typeof transistor switch to close it at the appropriate time.

Alternatively a combination of the first type and the second type oftransistor switches may be used in parallel together as the switches inthe implementation of the mixers 204,504 in the form of a fullycomplementary transfer or pass gate 904, such as a PFET 902 and an NFET903 with source and drains coupled together in parallel.

The PFET 902 includes a source terminal PS and a drain terminal PD forpoles of a switch, a gate terminal PG as the control terminal of theswitch, and a body terminal PB. The PFET body terminal PB in an analogtransfer gate connection is typically coupled to the PFET sourceterminal PS.

The NFET 903 includes a source terminal NS and a drain terminal ND forpoles of a switch, a gate terminal NG as the control terminal of theswitch, and a body terminal NB. The NFET body terminal NB in an analogtransfer gate connection is typically coupled to the NFET sourceterminal NS.

The transfer gate 904 includes an input terminal IN (e.g., PS and NS orPD and ND) and an output terminal OUT (e.g., PD and ND or PS and NS) aspoles of a switch, a pair of control terminals (e.g., NG and PG) ascontrol terminals of the switch, and a pair of body terminals (e.g., NBand PB). The NFET body terminal NB in an analog transfer gate connectionis typically coupled to the NFET source terminal NS. The PFET bodyterminal PB in an analog transfer gate connection is typically coupledto the PFET source terminal PS.

The p-type JFET 906 includes a source terminal S and a drain terminal Dfor poles and a gate terminal G for the control terminal of the switch.Similarly, the n-type JFET 907 also includes a source terminal S and adrain terminal D for poles and a gate terminal G for the controlterminal of the switch.

The PNP bipolar junction transistor (BJT) 908 includes a collectorterminal C and an emitter terminal for poles of a switch and a baseterminal for the control terminal of the switch. Similarly, the NPNbipolar junction transistor (BJT) 909 includes a collector terminal Cand an emitter terminal for poles of a switch and a base terminal forthe control terminal of the switch.

While the transistor switches have been described herein as beingswitched or turned on by various polarities of control signals coupledto the control terminal of the transistor, the level of voltage appliedto the control terminals may be set so that the transistors are turnedon differently. For example, the NFETs, PFETs, n-type JFETs, and p-typeJFETS may be turned on into a saturation (active) region or into atriode (linear or passive) region. Similarly, the bipolar junctiontransistors may be biased on into a forward-active region of operation.

The voltage levels of the respective control signals (e.g., the fourphased half duty cycle clock or local oscillating signals LO-I, LO-Ib,LO-Q, and LO-Qb) coupled to the control terminals of the switches areadjusted accordingly to the type of switches and their desired form ofoperation.

NFET Mixer Implementation

FIG. 2B illustrates a schematic diagram of an implementation of a mixersystem 200′. The mixer system 200′ includes the mixer 204′ implementedwith NFETs 903 along with an ideal current drive 202′, an ideal LOgenerator 208′, and a dual port load 206′ for simulating the mixer 204′.

The mixer 204′ includes NFETs 211A′-218A′ and 211B-218B′ coupledtogether as shown in FIG. 2B. The NFETs 211A′-218A′ and 211B-218B′ ofthe mixer 204′ respectively correspond to switches 211A-218A and211B-218B of mixer 204 described previously with reference to FIG. 2A.The function of the mixer 204′ is substantially similar to the functionof mixer 204 and is not repeated here for reasons of brevity.

FIG. 5B illustrates a schematic diagram of an implementation of a mixersystem 500′. The mixer system 500′ includes the mixer 504′ implementedwith NFETs 903 along with the ideal current drive 202′, an ideal LOgenerator 208′, and dual port load 206 for simulating the mixer 504′.

The mixer 504′ includes NFETs 511′-514′, 521A′-524A′, and 521B′-524B′coupled together as shown in FIG. 5B. The NFETs 511′-514′, 521A′-524A′,and 521B′-524B′ of mixer 504′ respectively correspond to switches511-514, 521A-524A, and 521B-524B of mixer 504 described previously withreference to FIG. 5A. The function of the mixer 504′ is substantiallysimilar to the function of mixer 504 and is not repeated here forreasons of brevity.

System Application

Referring now to FIG. 8, a radio system 800 is illustrated in which theembodiments of the inventive RF mixers described herein may be used. Theradio system 800 may be a mobile cellular telephone for example. Theradio system 800 includes a radio frequency RF circuit 802 coupled to anantenna 804. The RF circuit 802 may include one or both of an RFtransmitter 806 and an RF receiver 810R coupled to the antenna 804.

One or more mixers may be used as an upconverter 810T in the RFtransmitter 806. One or more mixers may be used as a downcoverter 810Rin the RF receiver 804. The quadrature four phase half duty cycle RFmixers described herein may be used as one or more instances ofquadrature mixers for the upconverter 810T and/or the downconverter801R.

Conclusion

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat the embodiments of the invention not be limited to the specificconstructions and arrangements shown and described, since various othermodifications may occur to those ordinarily skilled in the art. Instead,the embodiments of the invention should be construed according to theclaims that follow below.

What is claimed is:
 1. A radio frequency mixer system comprising: a fourphase clock generator to generate four phased half duty cycle clocks ofthe same frequency and each being out of phase by a multiple of ninetydegrees from the others; a dual differential electrical load having afirst differential input and a second differential input; and a fourphase half duty cycle mixer comprising a differential input port coupledto a differential input signal, an in-phase (I) differential output portcoupled to the first differential input of the dual differential load,and a quadrature-phase (Q) differential output port coupled to thesecond differential input of the dual differential load, wherein themixer comprises a plurality of first level switches coupled in parallelto the differential input port and a corresponding plurality of pairs ofparallel second level switches, each pair of parallel second levelswitches coupled in series to one respective first level switch and tothe dual differential output port, said first level and second levelswitches comprising control inputs coupled to the four phase clockgenerator to receive the four phased half duty cycle clocks, wherein thecontrol inputs of the first level switches are connected to first andsecond clock phases and the control inputs of the second level switchesare connected to third and fourth clock phases, and wherein the mixer isconfigured to convolve the differential input signal with the fourphased half duty cycle clocks to concurrently generate a differentialin-phase output signal on the in-phase differential output port and adifferential quadrature-phase output signal on the quadrature-phasedifferential output port.
 2. The radio frequency mixer system of claim1, further comprising: a differential signal source having adifferential output coupled to the differential input port of the fourphase half duty cycle mixer, the differential signal source to generatethe differential input signal in response to a non-differential inputsignal.
 3. The radio frequency mixer system of claim 1, wherein thedifferential input signal is a radio frequency differential inputsignal, the differential in-phase output signal is an intermediatefrequency differential in-phase output signal, and the differentialquadrature-phase output signal is an intermediate frequency differentialquadrature-phase output signal.
 4. The radio frequency mixer system ofclaim 1, wherein the differential input signal is an intermediatefrequency differential input signal, the differential in-phase outputsignal is a radio frequency differential in-phase output signal, and thedifferential quadrature-phase output signal is a radio frequencydifferential quadrature-phase output signal.
 5. The radio frequencymixer system of claim 1, wherein the plurality of first level switchesand the corresponding plurality of pairs of parallel second levelswitches are a first type of transistor closed by the application of ahigh voltage level upon its control terminal and opened by theapplication of a low voltage level upon its control terminal, a secondtype of transistor closed by the application of a low voltage level uponits control terminal and opened by the application of a high voltagelevel upon its control terminal, or a combination of the firsttransistor type and the second transistor type.
 6. A radio frequencymixer comprising: a plurality of first level switches comprising firstcontrol inputs and coupled in parallel to a differential input port; acorresponding plurality of pairs of parallel second level switchescomprising second control inputs and each pair of parallel second levelswitches coupled in series to one respective first level switch and to adual differential output port; and wherein the plurality of first levelswitches and the corresponding plurality of pairs parallel second levelswitches are configured to receive four phased half duty cycle clocks ofthe same frequency and each being out of phase by a multiple of ninetydegrees from the others, and wherein the first control inputs areconnected to first and second clock phases and the second control inputsare connected to third and fourth clock phases to convolve adifferential input signal on the differential input port with the fourphased half duty cycle clocks to concurrently generate a differentialin-phase output signal and a differential quadrature-phase output signalon the dual differential output port.
 7. The radio frequency mixer ofclaim 6, wherein the differential input signal is a radio frequencydifferential input signal, the differential in-phase output signal is anintermediate frequency differential in-phase output signal, and thedifferential quadrature-phase output signal is an intermediate frequencydifferential quadrature-phase output signal.
 8. The radio frequencymixer of claim 6, wherein the differential input signal is anintermediate frequency differential input signal, the differentialin-phase output signal is a radio frequency differential in-phase outputsignal, and the differential quadrature-phase output signal is a radiofrequency differential quadrature-phase output signal.
 9. The radiofrequency mixer of claim 6, wherein the plurality of first levelswitches and the corresponding plurality of pairs of parallel secondlevel switches are a first type of transistor closed by the applicationof a high voltage level upon its control terminal and opened by theapplication of a low voltage level upon its control terminal, a secondtype of transistor closed by the application of a low voltage level uponits control terminal and opened by the application of a high voltagelevel upon its control terminal, or a combination of the first type oftransistor and the second type of transistor.
 10. A method comprising:generating four phased half duty cycle clocks of the same frequency andeach being out of phase by a multiple of ninety degrees from the others;coupling the four phased half duty cycle clocks into a four phase halfduty cycle mixer; and switching switches in the four phase half dutycycle mixer in response to the four phased half duty cycle clocks toconvolve a differential input signal with the four phased half dutycycle clocks to concurrently generate a differential in-phase outputsignal and a differential quadrature-phase output signal on a dualdifferential output port, and wherein the switching comprises: switchingthe differential input signal based on first and second clock phases togenerate first level switching outputs; and switching the first levelswitching outputs based on third and fourth clock phases using aplurality of pairs of second level switches to generate the differentialin-phase output signal and the differential quadrature-phase outputsignal on the dual differential output port; wherein each pair of secondlevel switches receives one first level switching output.
 11. The methodof claim 10, wherein said switching comprises: in response to a firstphase of the four phased half duty cycle clocks, closing a first 1^(st)level switch and a first 2^(nd) level switch coupled in series to thefirst 1st level switch to pass through a signal on a positive RF inputterminal to a positive in-phase output terminal coupled into a firstdifferential load, and closing a third 1^(st) level switch and a fifth2^(nd) level switch coupled in series to the third 1st level switch topass through a signal on a negative RF input terminal to a negativein-phase output terminal coupled into the first differential load; inresponse to a second phase of the four phased half duty cycle clocks,closing the first 1^(st) level switch and a second 2^(nd) level switchcoupled in series to the first 1st level switch to pass through a signalon a positive RF input terminal to a positive quadrature-phase outputterminal coupled into a second differential load, and closing the third1^(st) level switch and a sixth 2^(nd) level switch coupled in series tothe third 1st level switch to pass through a signal on a negative RFinput terminal to a negative quadrature-phase output terminal coupledinto the second first differential load; in response to a third phase ofthe four phased half duty cycle clocks, closing a second 1^(st) levelswitch and a third 2^(nd) level switch coupled in series to the second1st level switch to pass through a signal on a positive RF inputterminal to a negative in-phase output terminal coupled into the firstdifferential load, and closing a fourth 1^(st) level switch and aseventh 2^(nd) level switch coupled in series to the fourth 1st levelswitch to pass through a signal on a negative RF input terminal to apositive in-phase output terminal coupled into the first differentialload; and in response to a fourth phase of the four phased half dutycycle clocks, closing the second 1^(st) level switch and a fourth 2^(nd)level switch coupled in series to the second 1st level switch to passthrough a signal on a positive RF input terminal to a negativequadrature-phase output terminal coupled into the second differentialload, and closing the fourth 1^(st) level switch and an eighth 2^(nd)level switch coupled in series to the fourth 1st level switch to passthrough a signal on a negative RF input terminal to a positivequadrature-phase output terminal coupled into the second differentialload.
 12. The method of claim 10, wherein each of the switches is ann-channel field effect transistor (NFET) closed by the application of ahigh voltage level upon its gate terminal.
 13. The method of claim 10,wherein each of the switches is a p-channel field effect transistors(PFET) closed by the application of a low voltage level upon its gateterminal.
 14. The method of claim 10, wherein each of the switches is ap-channel field effect transistors (PFET) and an n-channel field effecttransistors (NFET) coupled in parallel together, the PFET being closedby the application of a low voltage level upon its gate terminal and theNFET being closed by the application of a high voltage level upon itsgate terminal.
 15. An apparatus comprising: means for generating fourphased half duty cycle clocks of the same frequency and wherein each ofthe four phased half duty cycle clocks are out of phase by a multiple ofninety degrees from the others; means for convolving a differentialinput signal with the four phased half duty cycle clocks to concurrentlygenerate a differential in-phase output signal and a differentialquadrature-phase output signal on a dual differential output port, andwherein the means for convolving comprises: means for switching thedifferential input signal based on first and second clock phases togenerate first level switching outputs; and means for switching thefirst level switching outputs based on third and fourth clock phasesusing a plurality of pairs of second level switches to generate thedifferential in-phase output signal and the differentialquadrature-phase output signal on the dual differential output port; andmeans for coupling the four phased half duty cycle clocks into the meansfor convolving wherein each pair of second level switches receives onefirst level switching output.
 16. The apparatus of claim 15, wherein themeans for coupling the four phased half duty cycle clocks comprisesconductive traces in one or more layers of an integrated circuit. 17.The apparatus of claim 15, wherein the means for convolving comprises afour phase half duty cycle mixer including a plurality of first levelswitches coupled in parallel that each first level switch is coupled inseries to a corresponding pair of parallel second level switches thatare switched in response to the four phased half duty cycle clocks. 18.The apparatus of claim 15, wherein the means for generating the fourphased half duty cycle clocks comprises a clock generator.
 19. Theapparatus of claim 15, wherein the differential input signal is a radiofrequency differential input signal, the differential in-phase outputsignal is an intermediate frequency differential in-phase output signal,and the differential quadrature-phase output signal is an intermediatefrequency differential quadrature-phase output signal.
 20. The apparatusof claim 15, wherein the differential input signal is an intermediatefrequency differential input signal, the differential in-phase outputsignal is a radio frequency differential in-phase output signal, and thedifferential quadrature-phase output signal is a radio frequencydifferential quadrature-phase output signal.